1. Field of the Invention
The present invention relates generally to mechanical fasteners and, more particularly, to an improved locking fastener that is relatively insusceptible to inadvertent unfastening caused by vibrational or shock loading.
2. Discussion of Prior Art
A common problem with conventional mechanical fasteners is their susceptibility to inadvertent unlocking or unfastening as a result of vibrational or shock loading experienced by the fastener. It is known to provide fasteners with some means for enhancing or supplementing the pretension load traditionally generated by tightening the nut and bolt relative to one another. However, virtually all known attempts to develop a locking fastener that securely locks in a fastened condition are deficient for one reason or another. For example, several of the traditional locking fasteners are simply inadequate in restricting inadvertent unfastening of the fastener as a result of vibrational or shock loading. Additionally, a number of traditional locking fasteners are impractical because they are difficult to use or have complex and expensive constructions.
Furthermore, many of the known locking fasteners operate in such a manner that the fastener is limited to only one or, at the very most, relatively few applications. That is to say, traditional locking fasteners are commonly not reusable. This is often attributable to the fact that a portion of the fastener is stressed beyond its yield strength when used. One example of such nonelastic deformation is a locking nut having a plastic insert or coating covering the threads, such that the threads of the bolt "cut" into the plastic material. Although the insert or coating enhances the gripping force between the threads of the nut and the bolt, this type of fastener can only be used once. Another example of such a deficiency is a fastener having oversized bolt threads or undersized nut threads which enhance the locking power of the fastener yet significantly and quickly wear the threads of the bolt and nut.